Question 1073328
The wording is awkward.
" How far from Boston station have they met in two hours "
It's ungrammatical, but it sounds like they meet in 2 hrs
If this is true, then:
-------------------------
Let {{{ s }} = the speed of NY - BOS train in mi/hr
{{{ 2s - 10 }}} = the speed of the BOS - NY train in mi/hr
Let {{{ d }}} = distance in miles from Boston station when they meet
{{{ 220 - d }}} = distance from NY station when they meet
-------------------------------------------------------------
BOS - NY train:
(1) {{{ d = ( 2s - 10 )*2 }}}
NY - BOS train:
(2) {{{ 220 - d = s*2 }}}
----------------------------
By substitution:
(2) {{{ 220 - ( 2s - 10 )*2 = 2s }}}
(2) {{{ 220 - 4s + 20 = 2s }}}
(2) {{{ 6s = 240 }}}
(2) {{{ s = 40 }}}
and
{{{ 2s - 10 = 2*40 - 10 }}}
{{{ 2s - 10 = 70 }}}
-----------------------------
(1) {{{ d = ( 2s - 10 )*2 }}}
(1) {{{ d = 70*2 }}}
(1) {{{ d = 140 }}}
The trains meet 140 mi from the Boston Station
---------------------------------------------
check:
(2) {{{ 220 - d = s*2 }}}
(2) {{{ 220 - d = 80 }}}
and
{{{ 140 + 80 = 220 }}}
OK